Method of producing a hydraulic binder or thermoplastic containing product

ABSTRACT

A method for manufacturing an hydraulic binder or thermoplastic binder containing product including the steps of impregnating the binder into a flexible open cell polymeric foam element by compressing the foam element to exclude air from the open cells and then releasing the compression with the foam elements whilst in contact with the binder so that the binder penetrates and becomes contained in the open cells of the foam elements as it regains its shape. Alternatively impregnating the binder into the foam element from one side under pressure so that the binder penetrates and becomes contained in the open cells of the foam and then allowing the binder to set or hardened and dry to form the product. The product is particularly suitable as a building element.

BACKGROUND OF THE INVENTION

This invention relates to a method of producing a product from aflexible open cell polymeric foam element and a hydraulic binder slurry,and to the product so made. The product may be for example a panel or aboard or the like for use in the building industry.

Portland cement based building boards are well known. They are generallymade from cement bound particle board or the like, i.e they containlignocellulosic particles or fibres. These boards however suffer fromthe disadvantage that the lignocellulosic particles or fibres have apropensity to swell when water wetted and can interfere with the cure ofthe Portland cement. In addition, the manufacture of the boardsgenerally includes autoclaving, which is energy intensive.

Other types of hydraulic binder based building boards include those thatcontain expanded minerals such as vermiculite. The method of manufactureof such boards generally involves the use of pressure and temperature ina sophisticated production plant.

Another type of known boards are gypsum building boards which generallyinclude the use of paper liners.

Thus, while many types of hydraulic binder based building boards areknown, they generally suffer from one or other disadvantage. There isthus a need for a new type of hydraulic binder based product.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a methodof producing a product from:

-   -   (a) a flexible open cell polymeric foam element and    -   (b) a binder selected from:        -   (i) an hydraulic binder slurry; or        -   (ii) a mixture of a pozzolan and either lime or Portland            cement in the form of a slurry;        -   (iii) a synthetic geopolymer precursor slurry; or        -   (iv) a thermoplastic material in liquid form; which includes            the steps of:        -   (1) introducing the binder into the open cells of the foam            element by either:            -   (i) compressing the foam element to exclude air from the                open cells and then releasing the compression with the                foam element in contact with the binder so that the                binder penetrates and becomes contained in the open                cells of the foam element as it regains its shape; or            -   (ii) impregnating the binder into the foam element under                pressure so that the binder penetrates and becomes                contained in the open cells of the foam element; and        -   (2) allowing the binder to set or harden and dry to form the            product.

In one embodiment, in step (1), the foam element is submerged in thehydraulic binder slurry, and while submerged, the foam element iscompressed to exclude air from the open cells. The compression is thenreleased so that the slurry penetrates and becomes contained in the opencells. In a second embodiment of the invention, in step (1), thehydraulic binder slurry is applied to a surface of the foam elementprior to the foam element being compressed to exclude air from the opencells. In a third embodiment, in step (1), the hydraulic binder in drypowder form is placed on the foam element, which hydraulic binder isslurried with water, whereafter the foam element with the hydraulicbinder slurry thereon is compressed to exclude air from the open cells.

In a fourth embodiment of the invention, in step (1), the foam elementis compressed to exclude air from the open cells, and while compressedor as the compression is released, a hydraulic binder slurry is appliedto a surface of the foam element. As the compression is released and thefoam element regains its shape, the slurry penetrates and becomescontained in the open cells.

This step may be repeated.

The compression of the foam element in step (1) is carried out bypassing the foam element between a first roller and a surface, forexample a second roller. The hydraulic binder slurry is preferablyapplied to a surface of the foam element directly by at least one of thefirst and second rollers.

This may be achieved by providing the or each roller with a perforatedsurface for contacting a surface of the foam element and a hydraulicbinder slurry feed arrangement for feeding the hydraulic binder slurryto the perforated surface of the or each roller for application to asurface of the foam element.

In a fifth embodiment of the method of the invention the binder is fedunder pressure directly by one of the perforated rollers the binderpenetrating the open cells of the foam element from one side forcing theair out of the foam element from the opposite side without the foambeing compressed. Optionally this procedure may be repeated from theother side of the foam element as it is wound around a perforated rollerrevolving in the opposite direction to the first one and again withoutneed of compression.

It has also been found that thermoplastic materials can be used insteadof hydraulic binders in the method of the invention. Thus, the method ofthe invention as described above, in particular that described in thefourth and fifth embodiments of the invention, included producing aproduct from:

-   -   (b) a thermoplastic material

The thermoplastic material is preferably a thermoplastic compositionselected from the group consisting of polystyrene, polyethylene,polypropylene, polyvinyl chloride, polyvinyl acetal, A.B.S, bitumen, andrefinery bi-product, or any compatible combination, mixture or blendthereof.

In particular, the thermoplastic composition is a molten thermoplasticcomposition.

According to a second aspect of the invention there is provided aproduct comprising an open cell polymeric foam element containing a setbinder as described above in the open cells. The product is preferablymade by the method described above.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of an embodiment of the method of theinvention.

FIG. 2 is a schematic diagram of further embodiments of the method ofthe invention.

FIG. 3 is a schematic diagram of continuous, optionally simultaneous,pressure injection as used in the fourth embodiment of the method of theinvention.

FIG. 4 is a schematic diagram of continuous, optionally sequential,pressure injection as used in the fifth embodiment of the method of theinvention.

DESCRIPTION OF EMBODIMENTS

The first aspect of the invention is a method of producing a productfrom a flexible open cell polymeric foam element and a binder.

The first component is thus a flexible open cell polymeric foam element.

The preferred flexible open cell polymeric foam element is made from apolyurethane foam having a density in the range of from 6 kg/m³ to 40kg/m³, more preferably from 7 kg/m³ to 20 kg/m³ inclusive morepreferably from 7 to 12 kgs/m³. A particularly suitable flexible opencell polyurethane foam is one based on the combination of a toluenediisocyanate with a polyol, water, methylene chloride as a blowingagent, stannous octoate as a catalyst, and a surfactant which determinesthe cell size. Toluene diisocyanate is produced as two isomers, viz.2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate(2,6-TDI) and is commercially available as:

-   -   greater than or equal to 99.5% 2,4-TDI;    -   80% 2,4-TDI and 20% 2,6-TDI which is the most commonly used        product and is referred to hereinafter as TDI (80:20);    -   65% 2,4-TDI and 35% 2,6-TDI; and    -   “crude” TDI with an unidentified isomer ratio.

An example of a composition for use in making a flexible open cellpolyurethane foam is as follows:

80 parts TDI Toluene di-isocyanate and 20 parts MDIdiphenylmethanediisocyanate TDI (80:20) 578.7 Durapol 3000 (a polyol)675 Water 46 Silicone surfactant (Niax L/580) 19.6 33 LV (catalyst) 1.9Glycerine (crosslinker) 3.7 Methylene chloride (blowing agent) 166Stannous octoate (catalyst) 2.1 All parts by weight

The result is a TDI flexible open cell medium hard polyurethane foamwith a density of 10 kg/m³.

Other suitable polymeric foams include polyester foams, polyether foams,polyurethane polyester hybrid foams, and the like.

It is important that the polymeric foam element has a good “memory” sothat after it has been compressed, when the compression is released, thefoam element returns to substantially its original dimensions so thatthe binder can fill the open cells.

It is also important that the polymeric foam element has a suitablehardness as it is required to act as a carrier for the binder and act toas a re-inforcer therefor.

It is preferable that the polymeric foam cell size is not too small sothat the surface area of the foam is not too great. A cell size in therange 1 to 5.mm diameter is preferred giving a composite of excellentstrength at low densities.

As the polymeric foam element is flexible, the element may be postformed into a desired shape before the binder hardens. The shaping ofthe polymeric foam element containing the binder may take place in amould or maybe formed between the platens of a press or the like.

Alternatively, the polymeric foam element may be shaped before it comesinto contact with the binder. For example the polymeric foam element maybe produced in a block and then cut to a desired shape, e.g for theproduction of a fielded and planed door core, a shaped roof tile, or aboard with textured surfaces, before the binder is introduced, and whichshape is maintained by the “memory” of the foam, after the binder hasbeen introduced.

The second component is a choice of inorganic hydraulic binders asslurries in water binder.

The hydraulic binder is preferably selected from the group consisting ofPortland cement, the alpha and beta hemi-hydrates of calcium sulphate, acalcium aluminate cement, magnesium oxychloride, and magnesiumoxysulphate.

The hydraulic binder may be a Portland cement, preferably a rapidhardening Portland cement with a particle size of from 475 m²/kg orfiner. The Portland cement may be mixed with up to 15% by weight of anundensified silica fume with a particle size of about 20000 m²/kg.

When the hydraulic binder is the alpha or beta hemi-hydrate of calciumsulphate, it is preferably the beta-hemi hydrate of calcium sulphate,which is preferably finely ground, having a particle size of 300 whichmay be either synthetic or natural. This product is also referred to asgypsum.

When the hydraulic binder is Portland cement, the hydraulic binderslurry preferably contains 35 to 55 parts by weight of water to 100parts by weight of the Portland cement. When the hydraulic binder is thebeta hemi-hydrate of calcium sulphate, the hydraulic binder slurrypreferably contains from 55 to 130 parts by weight of water to 100 partsby weight of the binder.

The hydraulic binder slurry may include various optional additives asfollows:

-   -   1 a polyvinyl alcohol as an auxiliary binder, introduced in the        water. A suitable example is Mowiol 8/88 by Clariant.    -   2 An acrylic emulsion a methacrylate or a polyvinyl acetate,        added in the water, which increases water resistance, toughness        and flexural strength. An example is Acrylic Polymer E330 by        Rohm & Haas.    -   3 A super plasticiser in order to reduce the water to binder        ratio at a given viscosity. A suitable example is Melment F10 by        Hoechst, which is a melamine formaldehyde condensate.    -   4 A hydrophobic agent such as a silicone masonry water        repellant. A suitable example is BS 94 by Wacker which is an        anhydrous silicone based on hydrogen polysiloxane. When the        hydraulic binder is gypsum, it is preferably added to the gypsum        in an amount of about 0.3% by weight. Another suitable        hydrophobic agent, particularly for use with Portland cement is        BS 1307 by Wacker which is a silicone resin siloxane mixture        which is used in an amount of about 0.4% by weight.    -   5 A hydrate precursor or hydrogel such as Borax or an alkali        silicate respectively to improve performance in fire.    -   6 Reinforcing fibres of a maximum length of 1 mm such as        cellulose or polyamide.

The inorganic binder may also be a combination of a pozzolan and lime orPortland cement in a water slurry.

Suitable pozzolans include silica fume with a particle size in the rangeof from 5000 to 20000 m²/kg, ground granulated blast furnace slag with aparticle size in the range of from 300 to 2000 m²/kg, and fly ash with aparticle size in the range of from 300 to 2000 m²/kg, or a mixture ofany two or more thereof.

As stated above, the pozzolan must be combined with either lime orPortland cement as the source of calcium hydroxide. Generally there isused 95 to 75 parts by weight of the pozzolan to 5 to 25 parts by weightof the lime or Portland cement.

The inorganic binder may also be a synthetic goepolymer precursor inwater slurry. An example of a suitable geopolymer precursor is a blendof a metal oxide such as aluminium oxide or magnesium oxide with acalcium silicate, in the form of Wollastonite, the blend having aparticle size of 300 mesh or finer. In this case, the geopolymerprecursor is impregnated into the foam element in the form of a waterslurry. Thereafter the foam element containing the slurry is dried andthen post-impregnated with a compound selected from the group consistingof ammonium phosphate, phosphoric acid, or a solution of aluminiumphosphate and phosphoric acid, to form the geopolymer, viz. a magnesiumammonium phosphate hexahydrate.

The retention of the hydraulic binder slurry in foam elements where thecell sizes are relatively large is a function of apparent viscosity orrheology. In order to ensure a suitable rheology, silica fume may beadded to Portland cement, or suitable organic thickeners may be added toany of the hydraulic binders. Acrylic based thickener compounds arepreferred.

The first step of the method of the invention is to introduce thehydraulic binder slurry into the open cells of the foam element bycompressing the foam element to exclude air from the open cells and thenreleasing the compression with the foam element in contact with thehydraulic binder slurry so that the slurry penetrates and becomescontained in the open cells.

In one embodiment of the invention, the foam element is submerged in thehydraulic binder slurry and while submerged, the foam element iscompressed, whereafter the compression is released so that the slurrypenetrates and becomes contained in the open cells.

In the compression stage, the air in the open cells of the foam elementis forced out of the open cells. Thereafter, when the compression isreleased, the foam element, having a memory, returns substantially toits original size and shape, i.e the open cells open up again, allowingthe hydraulic binder to penetrate and be contained in the open cells.

It is not necessary to exclude all of the air from the open cells of thefoam element. Depending on the nature of the product to be manufactured,the amount of air to be excluded from the open cells can be determined.

The compression of the foam element is preferably carried out by passingthe foam element between a first roller and a surface, for example asecond roller.

This first embodiment of the invention is illustrated in FIG. 1.

Referring to FIG. 1, a flexible open cell polymeric foam element 10,which may be either a continuous sheet, or a discrete element, which maybe flat or shaped, is transported on a conveyor 12 into a slurry tank 14containing an agitator 16. The slurry tank 14 is filled with a hydraulicbinder slurry. The foam element 10 is passed between two rollers 18, 20between which the foam element 10 is compressed. On exiting the rollers18, 20 the foam element 10 regains its original size and shape and thehydraulic binder slurry penetrates and becomes contained in the opencells of the foam element 10. The foam element 10 now containing thehydraulic binder slurry passes out of the slurry tank 14 and is passedbetween two rollers 22, 24. The foam element 10 containing the hydraulicbinder slurry is compressed between the rollers 22, 24 to extract someof the hydraulic binder slurry therefrom. This hydraulic binder slurryis then fed back to the slurry tank 14.

The foam element 10 now containing the desired content of hydraulicbinder slurry is passed onto a conveyor 26 and then through a drier 28in which the hydraulic binder hydrates and sets and is dried. The finalproduct 30 then exits the drier 28.

In an alternative, before the hydraulic binder in the hydraulic binderslurry hydrates and sets, the foam element containing the hydraulicbinder slurry may be formed into a desired shape. For example, the foamelement containing the hydraulic binder slurry may be placed onto amould and then conformed to a shape such as a corrugated sheet orU-section or the like.

In a second embodiment of the invention, a hydraulic binder slurry maybe applied to a surface of the foam element. Then the foam element withthe hydraulic binder thereon is compressed to exclude air from the opencells and then the compression is released so that the hydraulic binderslurry penetrates and becomes contained in the open cells. Thecompression between the rollers or perforated compression plate orplates forces penetration of the hydraulic binder slurry into the opencells of the foam element. This step may be repeated in order to ensuresufficient penetration of the hydraulic binder slurry into the opencells of the foam element. This embodiment has the advantage thatweights and final product densities may be very accurately controlled ina batch production context.

A further embodiment of the invention is illustrated in FIG. 2 which is;

-   -   (i) to impose a shape upon the foam element containing the        inorganic binder slurry, and/or    -   (ii) to achieve a higher concentration of the inorganic binder        slurry at the surfaces of the foam element when compared with        the concentration of the organic binder slurry in the interior        of the foam element.

In terms of the second alternative, the foam element containing theinorganic binder slurry is compressed to impose a shape upon the foamelement, either on one or both sides of the foam element, which shape isretained when the inorganic binder sets.

This is illustrated schematically in FIG. 2, Referring to FIG. 2, a foamelement 10 impregnated with an inorganic binder slurry is conveyed froma slurry tank (not shown) on a conveyer 12 and then between top andbottom conveyors 14, 16 respectively, the conveyor 14 being shaped asillustrated, to impose a shape upon the foam element 10. The inorganicbinder impregnated in the foam element 10 must set sufficiently prior torelease from the conveyors 14, 16 so that the foam element 10 retainsits shape once it is moved out from between the conveyors 14, 16.

The shaped foam element 10 is then conveyed on a conveyor 18 into adrier 20, where the product is dried.

As an alternative, when the inorganic binder is for example a Portlandcement, the foam element 10 may be shaped between platens 22 which arethen stacked and/or clamped to allow the Portland cement to setsufficiently prior to removal of the foam elements 10 from the platens22, e.g for a period of 12 to 24 hours.

For example, the foam elements 10 may be allowed to hydrate fully overan extended period by stacking in an open area with or without steamcuring.

In the third alterative, the foam element containing the inorganicbinder slurry is compressed to increase the concentration of theinorganic binder at the surfaces of the foam element relative to theconcentration of the inorganic binder in the interior of the foamelement.

This is illustrated in FIG. 3 where there is shown a foam element 30having a higher concentration of inorganic binder 32 close to thesurfaces thereof relative to the concentration of inorganic binder 34 inthe interior of the foam element 30.

For example the foam element may initially have a thickness of 20 mmwhich is then compressed to a final thickness of 12 mm.

This is achieved as is illustrated schematically in FIG. 4. In FIG. 4A,there is shown an open cell 40 of a foam element containing an amount ofan inorganic binder 42. In FIG. 4B the same cell 40 is illustrated whenit has been partly compressed, indicating the concentration of theinorganic binder 42 in the cell. In FIG. 4C there is again illustratedthe same cell 40, now with an even greater concentration of theinorganic binder 42 in the cell 40.

In this way, it is possible to produce what is effectively a stress skincomponent with the highest concentration of the inorganic binder beingin the outer horizons of the component. This is also used forlamination.

The hydraulic binder slurry may be reinforced with thermoplasticpolymers chosen from acrylates, methacrylates, vinyls or polyvinylalcohol, or with water miscible thermosets such as oligo isocyanatessuch as Suprasec 1042 by Huntsman, or phenol formaldehyde resoles.

A fourth embodiment of the invention is illustrated in FIG. 5 which is;

Referring to FIG. 5, a flexible open cell polymeric foam element 10,which may be either a continuous sheet or a discrete element, which maybe flat or shaped, is transported on a conveyor 12 between two rollers14, 16 between which the foam element 10 is compressed.

The rollers 14, 16, in this embodiment, are revolving perforated hollowfeed tube rollers that include solid stationary cores 18, 20,respectively. The cores 18, 20 include respective feed conduits orchannels 22, 24 for conveying a hydraulic binder slurry to the rollers14, 16 and respective feed passages 26, 28 for feeding the hydraulicbinder slurry to the perforated surfaces 30, 32.

The hydraulic binder slurry then contacts the surfaces 34, 36 of thefoam element 10, whilst compressed and/or as compression is released,and then penetrates and becomes contained in the open cells of the foamelement 10 as compression is released on exiting the rollers 18, 20.

On exiting the rollers 18, 20 the impregnated foam element 10 regainsits original size and shape. The foam element 10 now containing thehydraulic binder slurry may be passed through a second set of perforatedhollow tube rollers 38, 40, where the abovementioned method may berepeated. In addition, the impregnated foam element 10 may be passedbetween an optional third set of hollow feed tube rollers 42, 44 whichonly partially compress the foam element 10 thereby resulting in partialimpregnation of the outer regions of the foam element 10 to formintegrated solid or semi-sold outer skins 46, 48. The foam element 10now containing the desired content of hydraulic binder slurry can thenbe further treated.

A potential difficulty in using the method referred to as the firstembodiment of the invention illustrated in FIG. 1 is that when water isadded to a hydraulic binder, hydration immediately commences and even ina continuous process the binder slurry in a bath or container will, in arelatively short period of time, produce lumps, accumulations orgranules of set or partly set hydraulic binder at different stages ofthe hydration process. In some cases, such as gypsum, the hydrationprocess can be almost indefinitely retarded, but this requires addedcost and at some point in the process, either the retardation must beneutralised or the hydration accelerated to overcome the retarder.

A further potential difficulty in impregnating the open cellular foam ina bath in which it is submerged is that when it is removed from thebath, the relatively high viscosity of the slurry on top of the emergingimpregnated foam means that it must be removed unless the sheet exitsthe bath vertically. This difficulty is particularly true of sheetmaterial.

In addition to obviating the above potential difficulties of submersionof the foam element, this fourth embodiment of the invention allows forthe degree of impregnation to be accurately controlled by pressure ofthe binder and the speed of the feed rollers. Further, the system isself-purging, preventing the accumulation of set or semi-set hydraulicbinder. Further, it makes provision for varying the reology or apparentviscosity of the slurry without process difficulty, because it is underpositive pressure and is forced into the foam. It also allows for theinclusion of a heavily or totally impregnated outer layer for addedstrength and water resistance of the final product. The system is easyto clean and easy to maintain and the binder can be easily maintained ata specific temperature by heating the stationary solid cores of theperforated rollers.

As indicated above, there may be used instead of the hydraulic binderslurry a thermoplastic material, typically a thermoplastic composition.The thermoplastic composition, which is preferably molten for ease ofprocessing, may be selected from the group consisting of polystyrene,polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetal,A.B.S, bitumen or refinery waste.

A fifth embodiment of the method of the invention is illustrated in FIG.6

An example of the introduction of a binder into the open cells of a foamelement by impregnation under pressure will now be given.

FIG. 6 is a schematic diagram of this method of the invention. A lengthof an open cell polymeric foam element 10 is passed between free rollingfeed rollers 12 which have a clutch controlled resistance so as to applya tension to the open cell polymeric foam element 10. The open cellpolymeric foam element 10 is pulled by a perforated feed roller 14,rotating in the direction shown. At the feed roller 14, a binder inslurry or liquid form is impregnated into the open cell polymeric foamelement 10 through a feed galley 16 in an assembly 18. As the binder inslurry or liquid form is injected into one side of the open cellpolymeric foam element 10, air in the open cells is exhausted from theother side of the open cell polymeric foam element 10.

Optionally, compression rollers 20 may compress the open cell polymericfoam element 10 to ensure uniform wetting and penetration of the binder.

The open cell polymeric foam element 10 now impregnated from one side isthen wound around a second perforated feed roller 22, rotating in theopposite direction to the feed roller 14. The feed roller 22 includes afeed galley 24 in an assembly 26 which injects the binder in slurry orliquid form into the opposite side of the open cell polymeric foamelement 10, with air again escaping from the side of the open cellpolymeric foam element 10 not being impregnated.

The assembly again may include compression rollers 28 to ensure uniformwetting and penetration of the binder.

The impregnated open cell foam element 10 is then deposited onto aconveyor 30.

Adjustable tension rollers 32 control the tension in the open cellpolymeric foam element 10 as well as the area of surface contact withthe perforated feed rollers 14 and 22.

The binder impregnated into the open cell polymeric foam element 10 isthen allowed to set to form the finished product.

As an alternative, the binder may be impregnated under pressure into theopen cells of the foam element from one side thereof only, the binderpenetrating through the entire thickness of the foam element

In another embodiment a binder precursor may be impregnated into theopen cells of the foam element from one side of the element by a firstfeed roller followed by the impregnation into the foam element of areactant to the binder precursor from the other side of the foam elementby a second or sequential roller.

As indicated in the previous embodiments, before the binder sets, thefoam element containing the binder may be formed into a desired shape.

In another embodiment of the invention, when the binder is a hydraulicbinder slurry, the hydraulic binder slurry may be foamed by any methodknown in the art, i.e. the use of a pre-formed foam on the use of afoaming agent that foams in situ to give a low density hydraulic binderslurry.

The resulting product has a low density and yet a high thermalinsulation and this is suitable for all thermal insulation applications,particularly the insulation of buildings.

Examples of products which may be produced by the method of theinvention include the following:

Gypsum Containing Products

A product moulded on both sides, such as the core of a fielded andplaned or multi panelled door, with a dry density in the range of from250 to 400 kg/m³ inclusive.

A product moulded to have a texture or pattern on one surface, such asan acoustic ceiling tile, with a dry density in the range of from 200 to300 kg/m³ inclusive.

Ceiling boards, wall boards and wall cores, particularly wall boardsreinforced with an acrylic to conform to the ASTM performance standardsfor wall boards without paper liners, with a dry density in the range offrom 400 to 600 kg/m³ inclusive, or more preferably laminated with paperon both sides by a thermoplastic polymer reinforced gypsum slurry.

Thermal insulation panels with a dry density in the range of from 100 to175 kg/m³ inclusive and an R value of 3.2.

Portland Cement Products

Siding where the foam element has been shaped to the requisite profileto produce a product with a dry density of about 800 kg/m³, which maythen receive a pure acrylic pigmented overcoat.

Splash backs with a density of about 900 kg/m³ and a typical thicknessof about 12 mm.

Corrugated roof sheeting where the form element containing the hydraulicbinder slurry has been shaped over a former to provide a corrugatedprofile, the product having a dry density of about 1200 kg/m³.

A roof tile with a dry density in the range of from 1200 to 1500 kg/m³.

A U-section gutter, having a thickness of 10 mm and a dry density ofabout 1400 kg/m³.

Another product which may be produced by the method of the invention islightweight aggregate, formed from chipped foam particles or granuleswhich may then be bound together by a hydraulic binder before or aftersetting, or by another binder after setting, and used as a castable orsprayable composition.

The foam element may be formed into particles or granules before cominginto contact with the hydraulic binder slurry. Alternatively the productmay be broken up after the hydraulic binder has set to give particles orgranules.

The density of the product is controlled by the following variables:

-   -   the cell size of the polymeric foam element;    -   the water to hydraulic binder proportion by weight in excess of        that required for full hydration of the hydraulic binder; and    -   the amount of the hydraulic binder slurry removed from the        saturated polymeric foam element during the method.

Densities of from 100 to 1500 kg/m³ are achievable with great accuracyby the method of the invention.

It is also to be noted that because the polymeric foam element has auniformity of cell distribution, the resulting product is also uniform.

In addition, dense surface skins of hydraulic binder may easily beincorporated into a product before setting of the hydraulic binder.

The method of the invention has various advantages. Firstly, it utilisessimple equipment which thus has cost implications. The method is alsoenergy efficient. The method allows density control of the finishedproduct over a wide range. Using the method of the invention it ispossible to produce a wide variety of finished products, with a varietyof shapes.

A particular advantage unique over other forms of foamed inorganicbinders is the peel strength, or resistance to delamination, oflaminated foam due to the penetration of the adhesive system to arequisite depth.

The method permits the production of products containing nolignocellulosic or other carrier fibres with their associateddisadvantages.

Examples of the invention will now be given.

EXAMPLE 1

An acoustic ceiling tile is made by the following method:

There is provided a 20 mm thick 10 kg/m³ density open cell flexible TDIpolyurethane foam element.

There is produced a hydraulic binder slurry containing: Beta hemihydratenatural gypsum fine grind 1200 2% solution of Mowiol 8/88 by Clariant -polyvinyl 800 alcohol in water solution Melment F10 super plasticiser byHoechst 10 Wacker BS15 potassium methyl siliconate 20 All parts byweight

The foam element is passed into a slurry tank containing the hydraulicbinder slurry composition set above and is compressed between tworollers. On release of the compression, the hydraulic binder slurrypenetrates and becomes contained in the open cells of the foam element.

The foam element containing the hydraulic binder slurry is passed out ofthe slurry tank and is rolled between two rollers to extract certain ofthe hydraulic binder slurry. The foam element containing the desiredquantity of hydraulic binder slurry is then passed through a drier wherethe hydraulic binder sets and the product dries. Thereafter the productis cut to size to produce a ceiling tile measuring 600×600×20 mm with adry density of 250 kg/m³.

EXAMPLE 2

A building board is made by the following method:

There is provided an 8 mm thick 14 kg/m³ density flexible open cell TDIpolyurethane foam element.

There is produced a hydraulic binder slurry containing: Rapid hardeningPortland cement 900 Silica fume undensified 100 Water 420 Acrylicemulsion 60 Melment F10 super plasticiser 10 Wacker BS1307 silicone base6 All parts by weight

The foam element is passed into a slurry tank containing the hydraulicbinder slurry composition described above. The foam element iscompressed between two rollers in the slurry tank. On release of thecompression, the hydraulic binder slurry penetrates and becomescontained in the open cells of the foam element.

The foam element containing the hydraulic binder slurry is passed out ofthe slurry tank. The Portland cement is allowed to hydrate and set,whereafter the product is dried to produce an 8 mm thick building boardwith a density of 900 kg/m³. The board is easy to cut and nail, can bemachined, is resistant to freeze/thaw and is cost effective.

1-17. (canceled)
 18. A method for manufacturing a product which includesthe steps of: a) engaging an open cell polymeric foam element with atleast a first perforated roller; b) feeding a binder through the firstroller; c) impregnating the binder into the foam element so that thebinder penetrates and becomes contained in the open cells of the foamelement; and d) allowing the binder to set to form the product.
 19. Amethod according to claim 18 wherein the foam element includes aflexible open cell polyurethane foam in the density range 7 to 20 kg/m³.20. A method according to claim 18 wherein the first roller includes aperforated surface through which the binder is delivered.
 21. A methodaccording to claim 20 wherein the first roller includes a feed passagewhere through the binder moves to the perforated surface.
 22. A methodaccording to claim 18 wherein the binder is selected from: i) anhydraulic binder slurry; ii) a mixture of a pozzolan and either lime orPortland cement in the form of a slurry; iii) a synthetic geopolymerprecursor slurry; and iv) a thermoplastic material in liquid form. v)23. A method according to claim 22 wherein the hydraulic binder slurryis selected from: i) alpha or beta hemihydrates of calcium sulphates;ii) Portland cement; iii) calcium aluminate; iv) a pozzolan with lime orwith Portland cement; v) magnesium oxichloride; and vi) magnesiumoxisulphate.
 24. A method according to claim 18 which includes the stepof compressing the foam element.
 25. A method according to claim 18which includes the step of shaping the foam element by molding, pressingor cutting.
 26. A method according to claim 18 which includes the stepof engaging the foam element with a second perforated roller.
 27. Amethod according to claim 18 which includes the step of engaging thefoam element with a first set of rollers consisting of the first andsecond rollers and at least a second set of rollers.
 28. A methodaccording to claim 18 which includes the step of drying the binderimpregnated foam element in a drier.